Automotive powertrains are becoming increasingly complex with the use of multiple electronic control units (ECUs) to control a wide range of powertrain functions and vehicular dynamics. In the control of modern diesel engines, for example, more sophisticated control units are being utilized to control the output of particular types of emissions such as NOx or smoke while also improving fuel economy and torque output. With the exception of a few, small-scale control units, the control calculations for many conventional powertrain systems are typically performed centrally using a single electronic control unit, often as one algorithmic calculation that computes variables across multiple subsystems.
Based on the increased sophistication demanded by modern powertrain subsystems, the ability of a single, centralized electronic control unit to adequately respond to each subsystem component is becoming increasingly difficult. The airside, aftertreatment, and transmission control subsystems of many modern vehicles, for example, often employ sophisticated control algorithms requiring numerous state variables to be solved for. In such case, the ability of the electronic control unit to rapidly and reliably compute factors such as torque output, catalyst loading, boost pressure, etc. may be compromised, affecting overall system performance. This is particularly the case as new and/or modified subsystem components are added to the powertrain system, causing the overall complexity of the control algorithm to increase. In some situations, the failure of a particular subsystem component, or a communications fault between the electronic control unit and a subsystem component, can also affect system performance.